1. Field of the Invention
The present invention relates to communication networks, and, in particular, to messages associated with link or node failures and/or setting up and tearing down connections in switches in communication networks.
2. Description of the Related Art
FIG. 1 shows a portion of a communication network 100. In particular, FIG. 1 shows four nodes labeled A, B, C, and D connected by five links labeled L1, L2, L3, L4, and L5. In order to transmit a data signal from Node A to Node C via Node B (i.e., along the path (A-B-C)), the switch fabric at Node B needs to be configured to route the signal received from Node A via Link L1 for transmission via Link L2 to Node C. Conventionally, this is accomplished by Node A transmitting a message to Node B instructing Node B to configure its switch fabric to make a connection that supports the desired communication channel from Node A to Node C. Such a message is referred to herein as a connection set-up request message, because the message contains a request for Node B to set up a connection.
If and when transmission of the signal from Node A to Node C is complete, Node A may transmit a connection tear-down request message to Node B requesting that Node B tear down the corresponding connection in its switch fabric in order to free up that portion of Node B's switch capacity for other communications.
Whenever a message is received at Node B, a component in Node B (e.g., a message decoder) processes the received message to decode and interpret the instructions contained therein (e.g., to determine whether the message contains a connection set-up request or a connection tear-down request). These instructions are then forwarded to another component in Node B (e.g., a switch fabric controller) that is responsible for implementing the instructions, e.g., to either set up or tear down a connection in Node B's switch fabric.
In conventional communication networks, there is a one-to-one correspondence between connection requests and connection request messaging. In other words, every time a different connection is to be set up or torn down, a different connection request message is transmitted from one node to another. Similarly, in conventional communication networks, there is a one-to-one correspondence between the receipt of connection request messages at a node and the forwarding of connection instructions within that node. In other words, every time a node receives a connection request message from another node, a single instance of instruction forwarding occurs, wherein the instruction contained in that message is forwarded to the node component responsible for implementing that instruction.
Such a messaging scheme may be acceptable for communication networks having relatively infrequent messaging and/or where the time that it takes to generate, transmit, and process such messages is not critical. There are situations, however, where a relatively large number of connection requests need to be implemented in a relatively short period of time. One classic example of such a situation occurs during service restoration processing following a failure in the communication network. In such situations, the prior art messaging scheme may not be acceptable.
Referring again to FIG. 1, assume that Link L2 suffers a catastrophic failure (e.g., a cut in the link) that prevents signals from being transmitted directly from Node B to Node C. In such a case, automatic restoration processing may be performed in order to quickly resume service that was interrupted by the failure in Link L2. In one possible implementation, this may involve re-routing all of the signals that were flowing along the path (A→B→C) to flow along the path (A→D→C) instead. In that case, Node D needs to be appropriately configured to provide all of the connections for all of the communications from Node A to Node C.
According to the prior art messaging scheme described above, this would involve the generation, transmission, and processing of a different connection set-up request message for each different communication channel. In general, there is a linear relationship between the number of connection request messages received by a node and the time that it takes for that node to complete all of the processing associated with those messages. If one connection request message takes X milliseconds to process, then 1000 connection request messages take about 1000X milliseconds to process. When the number of different connection request messages is sufficiently large, a node implementing the prior art messaging scheme might not be able to complete the restoration processing within the allocated time period.